1. Field of the Invention
The present invention relates to a process for producing aluminosilicate glass containing rare earth oxides, particularly yttrium oxide.
2. Description of the Prior Art
Aluminosilicate glass composed of silica and alumina has high heat resistance and good mechanical properties, and it is also superior in the corrosion resistance and weather-resistance. However, a very high temperature is required for the preparation of the glass of this type.
It was impossible to produce the glass of this type by a melting method by means of a usual electric furnace, since the usual electric furnace employing a silicon carbide heating element is restricted to a temperature of up to about 1550.degree. C.
In general, when an alkali metal oxide or an alkaline earth metal oxide is incorporated, the melting point decreases and it becomes possible to produce glass by means of a usual electric furnace equipped with a silicon carbide heating element. However, when an alkali metal oxide or an alkaline earth metal oxide is incorporated, there is a serious problem that various properties such as heat resistance, mechanical properties, chemical resistance, corrosion resistance and weather-resistance tend to be deteriorated.
The present inventors have previously reported that when Y.sub.2 O.sub.3 is incorporated, glass can be prepared by means of a usual electric furnace at a temperature of about 1550.degree. C. and the glass thereby obtained has excellent mechanical properties. However, isolated Y.sub.2 O.sub.3 is very expensive, and accordingly adds to the costs.